Interchangeable tooth crown



Nov. 13, 1956 H, MOYER INTERCHANGEABLE TOOTH CROWN Filed Oct. 14, 1954 1N VENTOR ATTORNEY 2 2,770,040 INTERCHANGEABLE TOOTH CROWN James H.Moyer, Columbus, Qhio, assignor to The C- lumbus Dental ManufacturingCompany, Columbus,

Ohio, a corporation of Ohio Application ()ctober 14, 1%54, Serial No.462,225 5 Claims. (Cl. 3212) This invention relates to artificial teeth,the same having particular reference to artificial teeth of the typeknown generally as jacket crowns.

Such crowns are formed to comprise hollow bodies of porcelain, or othertooth-forming materials, and, as presently employed, are adapted to beplaced on and around especially prepared, reduced crown regions ofnatural teeth. Jacket crowns of this type are particularly desirablewhen used in the restoration or replacement of natural teeth which areexposed to view upon normal opening of the mouth, as such jacket crowns,when expertly made and fitted in the mouth, present a most natural andattractive appearance. Such crowns are, however, at present severelyrestricted or limited in their general use in dental practice incomparison with other standardized and more economical but, in certainaspects, less desirable forms of artificial teeth. With a jacket crown arestoration is produced in which a prepared jawretained natural tooth isemployed as the base on which the crown is mounted, eliminating therebythe usual practice of removing fully from the jaw a defective naturaltooth to permit of the substitution therefor of the conventionalbacking-mounted, interchangeable, artificial tooth or facing of commonusage.

The relatively high cost of jacket crown restorations, as they are nowformed, is due primarily to the technical skill required by dentalspecialists to prepare correctly the crown portions of jaw-retainednatural teeth in adapting the same to receive such crowns. Another partof this cost is attributable to the skill required by dental technicianstrained in tooth molding and who usually are associated with dentalspecialists in producing jacket crowns. Another cost factor resides incrown formation which will not only conform to the physical requirementsof prepared natural teeth receiving the same, but will be so formed asto harmonize esthetically with the general form, color andcharacteristic markings of adjacent natural teeth. The absence of suchharmony is due in part to the fact that dental technicians seldom havethe opportunity of inspecting patients mouths to ascertain correct toothformations in which such jacket crowns are to be used. Because ofindividual variations in the preparation by dentists of the naturaltooth formations necessary in receiving jacket crowns, it has beendeemed impracticable for manufacturers of artificial teeth to producecommercially jacket crowns of standardized forms, hence the presenthigh-cost practice of individually making such crowns for each patientas the need therefor arises.'

In positioning jacket crowns in the mouth, a present practice followedby many dentists is to grind away the defective portions of the crownregion of a natural tooth to form what is known as a preparation for thereception of a jacket crown. Such a preparation usually possesses whencompleted an outwardly tapering form and is provided adjacent the gumline thereof with a ground in shoulder or ledge against which is seatedthe gingival edge surfaces of an associated jacket crown when the latteris applied to the preparation. The form and position of suchpreparation-provided shoulders constitute a variable which has beenanother deterrent'factor in precluding the factory manufacture ofproperly fitting, standardized, interchangeable jacket crowns. I g

It is a primary object of the invention to provide a standardized, lowcost, factory-produced jacket crown in States Patent 6 ice which theconstruction thereof is such as to enable the crown to be accuratelymounted on a simply and economically formed receiving preparationtherefor.

Another object is to provide a jacket crown having a hollow interiorwhich in part defines a receiving socket for the reception of a base ormounting preparation, and wherein the inner end of the socket isprovided, in predetermined relation to the gingival edges of the crown,with a shoulder formation adapted for the positive seating of the crownon a complemental preparation-carried shoulder formation.

A further object is to provide a jacket crown having a shoulderedpreparation-receiving socket, and one wherein the complemental shoulderon the receiving preparation is formed without grinding by a metallicband or collar fitted on and cemented to the preparation and received inthe socket of an associated jacket crown.

Another object of the present invention is to provide a standardized,factory made jacket crown which, as a result of its uniformpreparation-receiving socket construction, is adapted for use in thefield of prosthetic dentistry in capacities other than restorationsproduced on the prepared crowns of jaw-retained natural teeth, suchadded applications including the formation of abutment teeth for fixedreplacements, dummy teeth in dental bridges, thimble crown constructionsand in other capacities wherein an axially disposed preparation-typemounting for such jackets is advantageous. Therefore, by the term jacketcrown, I intend to include within its definition all such specificallydifferent uses to which the crown of the present invention isapplicable.

For a further understanding of my invention including additional objectsand advantages thereof, reference is to be had to the followingdescription and the accompanying drawings, wherein:

Fig. l is a perspective view disclosing my improved jacket crown, partsthereof being broken away and shown in cross section; I

Fig. 2 is a vertical transverse sectional view taken through the crownon substantially the line 2-2 of Fig. 1;

Fig. 3 is a vertical longitudinal sectional view of. the

crown taken substantially on the line 3-3 of Fig. 2;

Fig. 4 is a top plan view of the crown; Fig. 5 is a detail perspectiveview of a metallic moun ing band for the reception of an interchangeablejacket' crown of the present invention;

Fig. 6 is a vertical sectional view disclosing a jacket crown and bandwhen positioned on the prepared stub of a natural tooth and disclosing abody of impressionreceiving molding wax interposed between the adjacentinner surfaces of the band and the outer surfaces of the tooth stub; v

Fig. 7 is a detail sectional view disclosing the band with thestub-molded wax body thereon invested in a mold preparatory to removingor volatilizing the .wax body;

Fig. 8 is a similar view of the mold disclosing the cavity formationtherein developed as a result of the removal of the wax body; l i

Fig. 9 is a vertical sectional view similar to Fig. 6 and disclosing thefinal crown restoration;

Fig. 10 is a detail view of the crown when used on an abutment tooth;

Fig. 11 is a View in vertical section, showing the,

jacket crown as disclosed in the above-defined.figures of" the drawingsand by reference character identification of view of a bridge plug partsfound therein, the numeral designates the jacket crown of the presentinvention in its entirety. Preferably, the crown comprises a ceramicbody molded to provide artificial teeth for the individual or grouprestoration or replacement of natural teeth composed of centrals,laterals, cuspids, bicuspids and molars. Each of such crown types isfurther formed, as is customary in the commercial manufacture ofartificial teeth, to provide the same in various sizes, shapes,character markings and color characteristics. This is done so thatdentists will have at their disposal and selection a wide line of crownsfrom which one or more of such crowns will be available and in harmonywith the physical peculiarities of natural teeth of a patients mouthinto which the crown is to be mounted. Such crowns may be made from anysuitable materials adaptable for the formation of artificial teeth andby any standard process of manufacture. At present, I prefer that saidcrowns, when composed of ceramic materials and following moldingthereof, be fired while the same are maintained in an atmosphere inwhich negative pressures are caused to prevail. However, other standardprocesses and materials may be utilized advantageously and, therefore,the tooth crowns of the present invention are not limited to anyspecific composition or process of formation, except as hereinafterspecifically defined.

The material of each crown, in the process of molding the same, isformed to produce a substantially hollow crown body, having an internalchamber 16 open at the gingival or proximal region 17 of the crown andclosed at its incisal, occlusal, medial, distal, buccal or labial andlingual regions 18. The chamber 16 at the gingival end thereof isvolumetrically enlarged to provide a bandreceiving socket 19 havingground wall surfaces maintained within close dimensional limits ortolerances. The inner end of the socket terminates in a shoulder orledge 20 offset inwardly and laterally from the surfaces of the socketdisposed in substantially perpendicular relationship to the shoulder orledge. The latter is arranged approximately midway between the gingivaland incisal ends 17 and 18, respectively, of the crown and extendsentirely around its socket or chamber. The disposition of this ledge orshoulder in relation to the ground gingival edges 17 is mechanicallystandardized to exact dimensions in all crowns of a given series bygauged grinding operations performed by the tooth or crown manufacturer.It is this standard which in large measure accounts for theinterchangeability of the crowns of the present invention when used inthe month.

In connection with crowns so formed, I employ with each crown a mountingband or collar 21 composed, preferably of high-fusing, non-oxidizingprecious metals, including platinum and alloys thereof. Each of thesebands or collars is made to exacting dimensional standards,

so that it will fit closely into each of the crown sockets 19 adaptedfor the reception thereof. This is done in a manner enabling the inneredge of the band to be seated in engagement with the standardizedshoulder 20, and the outer wall surfaces of the band in close-fittingengagement with the ground inner wall surfaces of each socket 20 of acrown.

In forming one type of a preparation to receive the mounting band, anassociated natural tooth, indicated at 22, has its crown portionconveniently ground to present a prepared stub or stump 23 which may beof substantially tapering or frusto-conical form, the same being devoidof the usual ground-in shoulder formation around the gum line of thetooth which has hitherto been widely employed in jacket crown mountings.all that is required of the dentist in preparing a natural tooth for thereception of the jacket crown construction of the present invention, isthat the crown portion of the natural tooth be reduced 'in size so thatthe metal band or collar 21, which normally is supplied by themanufacturer with each jacket crown, and may fit loosely on In thisregard;

the stub preparation 23 receiving the crown. The dentist may thenexamine the temporarily inserted jacket crown to make color, size andconfiguration determinations,

thereby reaching a decision as to the applicability of a at 24 in Fig.6. The dentist may then place the crown 15,

with the band 21 positioned in the socket thereof, on the prepared toothstub or stump 23 in a correct position of application.

When the impression material 24 has set and caused to conform with thesurface pecularities of the tooth stub or stump on one side, and theinner surface configuration of the band of collar on its outer side, thecrown, its band and the impression compound are removed bodily andunitarily from the tooth stub. The band or collar is then carefullyremoved from its position in the crown socket in a manner avoidingmarring or deforming the wax compound.

As shown diagrammatically in Fig. 7, the collar, with the impressionmaterial thereon, is then placed in a conventional investment 25 andprovided with the usual sprue or sprues 26. The impression material,through the aid of heat, is then burned out or volatilized, producing inthe investment, immediately adjacent the band, a cavity 27 whichconforms precisely to the shape of impression material prior to itsvolatilization. This cavity is then pressure cast with a suitablecasting metal in a molten state. This may be done through one of thesprues or gates 26, so that the added metal is cast directly against theinner surface of the band or collar to unite upon solidification withthe latter and to thus produce a composite or final band or collar, asdisclosed at 28 in Fig. '9, which has an inner surface faithfullyconforming to the exterior surface of the tooth stump or stub 23 orother material or artificial base formation receiving the band orcollar. The latter will now accurately fit the prepared natural toothand may be cemented in operative position thereon. After removing anyexcess cement from the outer surfaces of the final band or collarfollowing the mounting thereof on the prepared tooth, the dentist willto secure another duplicative crown of the same series as the damagedcrown from his source of artificial tooth supply and substitute the, newfor the impaired crown. As the interior of each crown of 'a given seriesis mechanically standardized, the replacement crown will fit accuratelythe original band or collar which maintains its position on the naturaltooth at all times. Such crown substitution may be sively performed.

When the crown of the present invention is used as an abutment tooth oras a thimble crown, the dentist proceeds exactly in the same manner, asabove defined, in the formation and mounting of a jacket crown, except,

as shownrin Fig. 10, he will grind a substantially V' shaped cut,,-notch or slot 29 either mesially'or distally, or both, in a mannerexposing the band or collar in one I or bothareas for aisol'derattachment.

When the crown is used on a dental bridgc,as indi cated in Fig. ll, theprocedurewill be similar to its use as a thimble crown. V shaped cuts29'are' made at the gingival on both the mesial and distal areas of thecrown to expose a part of the band or collar 28 to provide quickly,conveniently and inexpensolder-receiving surfaces. In addition,accurately ground porcelain or other plugs 30 which will fit the insideof the band or collar are supplied by the crown manufacturer. Theseplugs can be ground at the gingival end of each to conform to ridgecontours and the complete restoration will .thus appear to be one of anallporcelain character.

In view of the foregoing, it will be apparent that the present inventionenables virtually any practicing dentist to produce and apply allporcelain jacket and thimble crowns in a properly fitting, mechanicallyperfected manner and to utilize from a Wide selection of possiblechoices the particular crown or crowns best suited for estheticconformity with the color, shape, size and characteristic .markings ofthe patients natural teeth. Then, in the event of breakage or damage ofthe originally applied crown, the present invention makes possible thequick, convenient and low-cost substitution of a new crown on theoriginal mounting band replacing the damaged one. By such means thepresent high costs of jacket crown restorations are capable of beingvery substantially reduced and brought within the range of presentlymore commonly employed restorations.

It will be noted that it is unnecessary in the mounting preparation ofthe crown of the present invention for a dentist to first grind in thetooth stump a precisely located seating shoulder, as has been the priorpractice. With the crown of the present invention the seating shoulderis carefully formed by the manufacturer in the interior of the crownitself, thus eliminating one of the outstanding difficulties hithertofaced by dentists; namely that of accurately grinding the seatingshoulder on a natural tooth stump to be received in the chamber of ajacket crown. For the further convenience of the dentist each metallicband or collar 21 is formed by the manufacturer and supplied commonly tothe dental profession with the particular crown adapted to receive thesame. The dentist is thus merely required to grind the natural toothstub or stump 23 until the band will fit loosely and with some playthereon. The wax or other molding material is then applied to the innersurface of the band and placed on the prepared tooth stump so that themolding material will produce in its inner face a true pattern of thetooth stump. This pattern, while contained in the band and protected andreinforced thereby, is placed in the investment 25.

Following cavity formation in the investment, after the wax has beenburned out of the same, additional metal is cast into the cavity left asa result of the burning or volatilization of the molding material, thenew metal being cast directly against the band. This operation enablesthe inside of the band to be truly formed so that it will fit perfectlyon the prepared tooth stump adapted to receive the same. Further, sincethe wax in my preferred procedure is at all times reinforced by the bandduring the operation of placing the same in pattern-forming engagementwith the tooth stump, followed by the removal of the band and waxpattern from the stump and investing the same in a mold, there is littlelikelihood of accidentally deforming the pattern.

The present invention thus enables such jacket crown of a dentalrestoration to be readily produced, provides ready crowninterchangeability, and enables a restoration to possess an appearancewhich constitutes an improvement over that heretofore produced by arelatively few highly skilled dentists who have specialized in such afield of practice.

As previously indicated, the jacket crowns of the present invention maybe employed in various capacities to which, so far as I am aware, custommade jacket crowns of the prior art have not been adapted. While, ofcourse, my standardized jacket crown finds a wide field of use in singletooth restorations in which the jacket crown is mounted on a preparationin the form of a natural tooth stub, and to which I have referred inconsiderable detail, yet it is, also, well adaptable as abutment, bridgeand dummy teeth constructions or in other original dental replacementsas it is in restoration practice.

I claim:

1. Jacket crown construction for dental bridges, comprising: a moldedheat-hardened body, said body including an internal cavity closed on allsides thereof and terminating in a cervical extension which opens to thegingival end of the body, said cavity being formed with an inwardly andlaterally projecting shoulder placed in predetermined spacedrelationship to the open end of said extension; a metallic mounting bandpositioned in said extension for close-fitting cemented engagement withthe walls thereof, said band having an edge thereof arranged in seatingcontact with said shoulder; and a stationary mounting plug axiallydisposed within said band for cemented union therewith.

2. A jacket crown comprising a dentiform body adapted for placement on aprepared natural tooth, said body having a closed internal cavity of asize to receive freely such a tooth, the cavity being formed with acervical extension of uniform diameter throughout its length and whichopens to the gingival end of the crown; an inwardly and laterallyprojecting positioning shoulder formed at the inner end of saidextension, said shoulder occupying a plane substantially perpendicularto that of the side walls of the cavity extension midway of the lengthof the cavity and in inwardly spaced determinate relation from thegingival end of the crown; and a cylindrical metallic band adapted formounting on a prepared tooth formation, said band being positionedwholly within the confines of said extension for close-fitting cementedengagement of its outer wall surfaces with the side wall surfaces of theextension and having its inner end disposed in seating, thrust-receivingengagement with said shoulder.

3. A jacket crown as defined in claim 2, and wherein the inner surfacesof the band conform to the configuration of the prepared natural toothon which the band is to be mounted.

4. A jacket crown for use on dental preparations, comprising: a bodyformed with an internal cavity having a cervical extremity open to thegingival end only of the body, said cavity being formed with an inwardlyand laterally projecting shoulder disposed intermediately of the depthof the cavity in predetermined spaced relation to the gingival edgesdefining the open end of the cervical extremity of said cavity; and ametallic mounting formed for application to a natural tooth prepared toreceive the same for the support of said crown, said shoulder havingengagement with an outer end of said mounting, the shoulder of the crowncavity being disposed in a single plane perpendicularly intersecting thelongitudinal axis of the cavity.

5. A jacket crown comprising a dentiform body adapted for placement on aprepared natural tooth, said body having a closed internal cavity of asize to receive freely such a tooth, the cavity being formed with acervical extension of uniform diameter throughout its length and whichopens to the gingival end of the crown; and an inwardly and laterallyprojecting positioning shoulder formed at the inner end of saidextension, said shoulder occupying a plane substantially perpendicularto that of the side walls of the cavity extension midway of the lengthof the cavity and in inwardly spaced determinate relation from thegingival end of the crown.

References Cited in the file of this patent UNITED STATES PATENTS640,551 Fones Ian. 2, 1900 1,248,242 Babcock Nov. 27, 1917 1,425,055Rose Aug. 8, 1922 2,327,548 Pearlman Aug. 24, 1943

